Terminal construction



Sept, 11, 1934. J. E. SMITH "TERMINAL CONSTRUCTION Filed Nov. 3, 193,2

M Z: %1z i m 37 wm gm ZZZYK S Patented Sept. 11, 1934 PATENT OFFICE1,973,271 TERMINAL CONSTRUCTION JohnE. Smith, Bellevllle, Ill., assignorto Knapp- Monarch Company, Belleville, 111., a corporation of MissouriApplication November 3, 1932, Serial .No. 641,016

2 Claims. (01. 173-269) An object of my present invention is to providea simple and durable terminal construction which is inexpensive tomanufacture and assemble and involves a minimum of parts.

A further object is to provide a terminal construction especiallyadapted for heating elements and which provides an effective electricalconnection between the terminal wire or a heating element, or anyelectric apparatus, and a terminal screw and at the same time providesan insulated mounting for the terminal screw which is especially adaptedfor connection with a tubular casing or for positioning in an opening ofa supporting element.

Still a further object is to provide aninsulated terminal construction,which, besides providing an electrical connection between a terminalwire and a, terminal screw, effects a tightening action of a bushingwithin a'tubular casing or opening so that the terminal construction isretained relative to its;support.

A further object is to provide a combination bushing tightening andterminal screw with means to grip an electric terminal wire and effeet asubstantial electrical connection therewith.

Still a further object is to provide a terminal construction including alongitudinally slotted screw for a terminal wire to extend through, thewire extending out of the slot and encircling the screw and a nut beingprovided for engaging the encircling part of the wire to make electricalconnection therewith.

Still another object is to provide a tapered screw associated with asplit bushing for expanding the bushing in its mounting when the screwis tightened, thus causing it to be frictionally retained relative tothe mounting.

With these. and other objects in view my invention consists in theconstruction, arrange- 'ment and combination of the various parts of mydevice, whereby the objects contemplated are attained, as hereinaftermore fully set forth, pointed out in my claims, and illustrated in theaccompanying drawing, in which:

Figure 1 is an enlarged view partly in longitudinal cross section of aheating element with a pair. of my terminal constructions appliedthereto.

Figure 2 is a sectional view of a terminal construction havingadditional features.

Figure 3 is a perspective view of a terminal screw used in myconstruction.

Figure 4 is a sectional view showing a modified 551cm 0! terminalconstruction.

Figure 5 is a, sectional view on the line 5-5 of Figure 4. I

Figure 6 is a sectional view showing the construction of Figure 4 in aslightly modified shapef Figure '7 is a sectional view on the line 7-7of Figure 6; and

Figure 8 is a side elevation of the terminal screw shown in Figure 6illustrating it in the shape it is formed before it is used.

On the accompanying drawing, I have used the reference numeral 10 toindicate a tubular casing. Within the tubular casing, a heating element12 is shown, the space between the heating element and the casing beingfilled with insulating material 14 so as to insulate the heating elementrelative to the casing.

My terminal construction includes a bushing 16 adapted to flt into theend of the tubular casing 10, a terminal screw 18 and a draw nut 20. Thebushing 16 may be of shouldered construc- 7 tion as illustrated so as tolimit its inward movement relative to the casing 10.

The bushing 16 has a bore 22 through which the terminal screw 18extends. The terminal screw is longitudinally slotted, as indicated at24, 30 the slot extending through the head of the screw and into theshank thereof at least past the outer end of the bushing 16.

The heating element 12 has a terminal wire 26 adapted to extend throughthe slot 24 and then encircle the screw 18 as indicated at 26a. A cupwasher 28 is preferably-provided to receive the encircling portion 261:of the terminal wire 26.

The nut-20 is adapted to be tightened against the encircling portion 26aof the terminal wire 26 and if desired, a washer 30 may be interposedbetween the nut 20 and the encircling portion or the wire. In additionto the nut 20, a terminal nut 32 may be provided for tightening againsta supply wire 34. The slot 24 provides a convenient passageway for theterminal wire 26 to the nut 20 where it is secured. Thus the nut 20serves the combination pu p se 01' tightening the screw 18 relative tothe bushing 16 and engaging the terminal wire 26 to clamp it between thebushing and the nut and thus provides an eflicient electrical connectionbetween the'terminal wire and the terminal screw.

As shown in Figure 2, the bushing 16 is replaced 1 -by a bushing 160.which is shown as being of slightly diiierent shape. It is countersunkas indicated at 18a to receive the head of the screw 18. This bushing isadapted formounting in an opening36 of a supporting member 38, aretainer 40 being provided to retain the bushing relative -to thesupport.

- which differs from the bushing 16 in having a bore 22b which istapered. Furthermore, the bushing 16b is a split bushing, it being madeof two parts as shown in Figure 5.

The terminal screw 18b is tapered to fit the tapered bore 22b of thebushing 16b.

The construction shown in Figures 4 and 5 provides means for the nut 20to serve the combination purpose of engaging the terminal wire 26 andtightening the bushing 16b relative to the tubular casing 10 byexpanding the two parts thereof when the draw nut 20 pulls the taperedscrew 18b into the tapered bore 22b.

In Figures 6, 7 and 8, I have shown another way of providing'a bushingtightening means operable by tightening the terminal screw. In thesefigures, a terminal screw 180 is shown having a transverse slot 39. Theends, as indicated at 39a, are flared.

When the draw nut 20 is'tightened, the flared ends 39a will engage thecorners 17 of a split bushing 16c and will both tend to spread the splitbush ing and contract the slot 39 to the position shown in Figure 6.

With the terminal wire 26 extendinginto the slot, it is thereby tightlyclamped and frictionally held relative to the terminal screw withoutextending to the exterior of the bushing 16c and there encircling thescrew. As shown in Figure 7, the bushing 160 may be merely split on oneside instead of being split completely transversely as the bushing 16bin Figure 5. In either case, there will be an expanding tendency for thebushing to tighten then relative to its support which in Figures 6 and 7is shown as a tube.

It has always been a problem to provide a good electrical connectionbetween aheating or electrical resistance wire and a terminal. Byextending the wire longitudinally through the slot, it contacts with thescrew throughout the length of the slot so that there is electricaltransfer of energy throughout the slot which prevents the encircling end26a from becoming red hot like the heating portion of the heatingelement. Also the between the terminal screw and the terminal wire.

Such changes as suggested and others might be made in the constructionand arrangement of the parts of my device without departing from thereal spirit and purpose of my invention, and it is my intention to coverby my claims, any modified forms of structure or use of mechanicalequivalents, which may be reasonably included within their scope.

I claim as my invention:

1. In a terminal construction, a tubular bushing of insulating material,a terminal screw therethrough having a head on one end and threaded onits other end, said terminal screw being longitudinally slotted toreceive a current carrying wire through said head and through saidbushing when said screw is assembled relative thereto, a nut on thethreaded portion of said terminal screw for drawing said terminal screwlongitudinally through said bushing with said head engaging one endthereof and a wire in said slot of said terminal screw and having itsterminal end extending out of said slot, around said screw andinterposed between said nut and said bushing.

2. In combination with a casing having an opening therein, a terminalconstruction comprising a tubular bushing of insulating material in saidopening, a terminal screw through said bushing having a head on one endand threaded on its other end, said terminal screw being longitudinallyslotted to receive a current carrying wire through said head and throughsaid bushing when said screw is assembled relative thereto, a nut on thethreaded portion of said terminal screw for drawing said terminal screwlongitudifoo nally through said bushing with said head engaging one endthereof and a wire in said slot of said terminal screw and having itsterminal end extending out or said slot, around said screw andinterposed between said nut and said bushing.

, JOHN SMITH.

